Hi there , i use google translate to you. In Blender 1 blender unit = 1 mm , you need to use this script for measure http://www.ewocprojects.be/chromruler.html ctrl+shit+r to go in ruler mode shift+ left click to add and measure.

When you upload to Shapeways you set : mm and will be ok. "Orientation Bounds" measure is to make the moldel fit in some space, the real measures are first.